Hi all,

I'm working on Atheros ar9331 related patches for upstream. Suddenly
this architecture is not working with latest mips_4.21 tag. Bisecting is
pointing to dma-mapping-4.20 merge.

The symptoms are following:
- networking is broken, getting tx timouts from atheros network driver.
- depending on configuration boot will stall even before UART is enabled
- after reverting some of dma-mapping patches, network seems to work but
init will trigger segfault. It is running from nfs-root.


First patch where regressions started is this:
commit dc3c05504d38849f77149cb962caeaedd1efa127
Author: Christoph Hellwig <hch@lst.de>
Date:   Fri Aug 24 10:28:18 2018 +0200

    dma-mapping: remove dma_deconfigure

    This goes through a lot of hooks just to call arch_teardown_dma_ops.
    Replace it with a direct call instead.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Robin Murphy <robin.murphy@arm.com>

It is not enough to revert this patch. This rework seems to be huge.

I also tested dma-mapping-4.21 tag, with same result.
In case, some one won't to play with it, the patches can be found here:
https://github.com/olerem/linux-2.6/commits/v4.20/topic/ath79-upstream-2019.01.04.1


It will be great if some one can help me to troubleshoot this issue.

-- 
Regards,
Oleksij